The present invention relates to live roller conveyor systems for transporting articles along a predetermined path. More specifically, this invention relates to live roller, line shaft conveyor systems which utilize the frictional coupling between a drive shaft and at least one torque tube-pulley assembly to provide power to a series of conveyor rollers.
Live roller conveyor systems are well known in the art. In general, these systems include a series of driven rollers which lie within a common plane. The driven rollers form a pass line along which articles are conveyed. Prior art conveyor systems have employed various means for driving the conveyor rollers in order to convey the articles to a collection or accumulation location. Typically, a live roller conveyor system includes a rotatable drive shaft and means for transferring power from the rotating shaft to the conveyor rollers. The rotating conveyor rollers convey the articles along the pass line until they have reached an accumulation location where the rollers are stopped to allow for the accumulation of the articles.
One such prior art conveyor system is described in U.S. Pat. No. 3,696,912 (Fleischauer et al.), the disclosure of which is incorporated by reference herein. In general, the '912 patent describes a conveyor system which includes individually powered transverse rollers disposed within a common plane defining a pass line along which the conveyed articles are propelled. In one embodiment, a plurality of end-to-end elongate sleeves are positioned along the length of the drive shaft. Each elongate sleeve carries a plurality of drive pulleys which transfer power from the drive shaft to the associated rollers through resilient tensioned drive belts. The drive belts pull the pulleys and the sleeves upward thereby providing frictional coupling between the pulleys, the sleeves, and the drive shaft. This frictional coupling is generally sufficient to provide power transmission from the drive shaft to each roller. The use of elongate sleeves allows groups of rollers to be braked simultaneously by halting the rotation of the sleeve while the drive shaft continues to rotate. In another embodiment of the '912 patent, spool shaped depressions are provided directly within the outer surface of each elongate sleeve.
The various embodiments disclosed in the '912 patent are generally suitable for transmitting power to the individual rollers. However, the embodiments of the aforementioned patent have several disadvantages. The use of unitary elongate sleeves is generally disadvantageous since the sleeves are manufactured in predetermined uniform lengths thereby inhibiting flexibility of design in those instances where sleeves of nonuniform lengths would be desirable. Additionally, while the system is operating, the entire length of each elongate sleeve is in constant frictional contact with the drive shaft. This frictional contact results in significant heat generation which can shorten the useful life of the sleeves.
Another prior art system is shown in U.S. Pat. No. 3,621,982 (Fleischauer et al.), the disclosure of which is incorporated by reference herein. The '982 patent generally describes a conveyor roller system wherein each conveyor roller is individually powered. In one embodiment, a plurality of pulleys are individually disposed along the length of the drive shaft with spacer members loosely interposed between each pulley pair. As in the aforementioned '912 patent, an elastomeric drive belt connects each pulley to an individual conveyor roller. The belt pulls the pulley to one side of the drive shaft to provide frictional coupling between the drive shaft and the pulley for a non-slipping transmission of power from the drive shaft to each conveyor roller.
The use of individual pulleys, loosely disposed along a drive shaft, generally requires fairly elaborate braking means to brake a group of rollers simultaneously. Additionally, the drive for the individual pulley/conveyor roller pairs does not contribute to the drive for any of the other pulley/roller pairs in the system. Such a contribution, referred to as "positive drive", is desired as an aid in loading heavier articles onto the pass line.
Similarly, U.S. Pat. No. 3,650,375 (Fleischauer et al.) generally discloses drive pulleys individually disposed along a drive shaft with spacers interposed therebetween. The disclosure of the '375 patent is incorporated by reference herein. In the embodiments of the '375 patent, the means for driving the conveyor rollers does not include a "positive drive."
The present invention overcomes the aforementioned problems of the prior art systems. Specifically, an interlocking torque tube-pulley assembly is provided for live roller, line shaft conveyor systems. The assembly is axially disposed along a rotating drive shaft and includes a number of drive pulleys with spacer members interposed therebetween. The drive pulleys and spacer members snap together by an overlap of materials with a locking feature. With the pulley and spacer members snapped together, an "accumulation zone" of conveyor rollers is formed. Within this zone, conveyor rollers are simultaneously driven by endless drive belts which connect each of the pulleys to individual conveyor rollers. In this arrangement of parts, the drive belts maintain the pulleys, which are part of the assembly, in frictional contact with the drive shaft to provide the necessary transmission of power from the drive shaft to the conveyor rollers.
The interlocking design of the present invention provides a "positive drive" within each accumulation zone which is valuable in situations, for example, when an object to be conveyed is first entering the conveyor line. In such instances, the additional drive provided by the other pulley/roller pairs enables heavier packages to be pulled onto the pass line by the first one or so rollers in the accumulation zone. Additionally, zone lengths can be varied according to the requirements of a specific job without the need to manufacture and store unitary assemblies of various lengths. In an alternate embodiment, variations in the spacing between the conveyor rollers can be accommodated by providing segmented spacer members with collars whereby the distance between the pulleys can be varied by use of a collar to join two spacer half portions.
The components of the present invention can be manufactured out of steel or a suitable non-ferrous metal, or a heat resistant synthetic material. In general, steel, or another metallic material, is more efficient in dissipating the heat which is generated by the friction between the drive shaft and the assembly. In general this heat tends to shorten the useful life of the drive pulleys. Assemblies manufactured from steel or a non-ferrous metal generally have longer useful lives than assemblies made from synthetic materials.
The problem of heat dissipation with synthetic components can be minimized in several ways. Spacer members may be made so that, when connected to a pulley pair, the spacers do not contact the rotating drive shaft. In this manner, frictional contact between the drive shaft and the spacer members can be avoided. Furthermore, the placement of drill holes in the spacer members will allow heat to dissipate therethrough. When synthetic materials are used, the choice of material can also have an affect on the longevity of the assembly. Various known heat-resistant synthetic materials are satisfactory for the manufacture of the assembly components. In particular, the use of an acetal resin, such as the acetal resin known under the trade name "Delrin", is quite satisfactory for producing a thermally stable assembly. The use of nylons, however, has been generally unsatisfactory in overcoming the effects of heat generation on the component pieces of the assembly.
The interlocking assembly is provided with an overlap of parts. A snap/lock feature is provided to releasably secure the component pieces of the assembly to each other to provide for "positive drive", and the like. The assembly of the present invention allows for the simultaneous braking of all conveyor rollers within an accumulation zone by simply applying sufficient braking force to one of the spacer members, for example, to stop the assembly from rotating. Braking is generally accomplished in a manner well known to the art, such as by using a clamp type brake which is either pneumatically or electrically activated.
Accordingly, it is an object of the present invention to provide a live roller, line shaft conveyor system wherein an interlocking torque tube-pulley assembly is utilized.
It is another object of the present invention to provide an interlocking torque tube-pulley assembly for live roller, line shaft conveyors wherein pulleys are positioned along the length of a drive shaft with a spacer member interposed between and connected to at least one of the pulleys.
It is still another object of the present invention to provide a live roller, line shaft conveyor system including an interlocking torque tube-pulley assembly positioned along the drive shaft of the system wherein an accumulation zone can be braked by applying braking pressure along the length of the assembly, preferably along one or more of the spacer members.